At times, we would like to extract the audio from an MP4 video file. To do this in Linux, open a terminal window in Ubuntu and use the utility called avconv as follows:
avconv -i MyVideoFile.mp4 -vn -acodec copy MyAudioFile.aac
where, MyVideoFile.mp4 is your mp4 video file. You can then listen to the MyAudioFile.aac on any music player.
avconv is the replacement for ffmpeg on Ubuntu 14.04. To install avconv, do the following:
sudo apt-get install libav-tools <enter>
Remember, avconv is as powerful as ffmpeg.